In various open and laparoscopic surgeries, it is necessary to seal or weld the margins of transected tissue volumes and transected blood vessels. However, satisfactory instruments have not been developed for electrosurgically excising a tissue biopsy sample from a lung or liver, for example, that seal the margin of the targeted structure while at the same time preventing gross thermal damage to the resected tissue sample.
As background, various radiofrequency (Rf) surgical instruments have been developed for sealing the edges of transected tissues. For example, FIG. 1A shows a sectional view of paired electrode-jaws 2a and 2b of a typical prior art bi-polar Rf grasper grasping two tissue layers. In a typical bi-polar jaw arrangement, each jaw face comprises an electrode and Rf current flows across the tissue between the first and second polarities in the opposing jaws that engage opposing exterior surfaces of the tissue. FIG. 1A shows typical lines of bi-polar current flow between the jaws. Each jaw in FIG. 1A has a central slot adapted to receive a reciprocating blade member as is known in the art for transecting the captured vessel after it is sealed.
While bi-polar graspers as in FIG. 1A can adequately seal or weld tissue volumes that have a small cross-section, such bi-polar instruments are often ineffective in sealing or welding many types of anatomic structures, e.g., (i) anatomic structures having walls with irregular or thick fibrous content, such as lung tissue; (ii) bundles of disparate anatomic structures, and (iii) substantially thick anatomic and structures.
As depicted in FIG. 1A, a prior art grasper-type instrument is depicted with jaw-electrodes engaging opposing side of a tissue volume with substantially thick, dense and non-uniform fascia layers underlying its exterior surface. As depicted in FIG. 1A, the fascia layers f prevent a uniform flow of current from the first exterior tissue surface s to the second exterior tissue surface s that are in contact with electrodes 2a and 2b. The lack of uniform bi-polar current across the fascia layers f causes non-uniform thermal effects that typically result in localized tissue desiccation and charring indicated at c. Such tissue charring can elevate impedance levels in the captured tissue so that current flow across the tissue is terminated altogether. FIG. 1B depicts an exemplary result of attempting to create a weld across tissue with thick fascia layers f with a prior art bi-polar instrument. FIGS. 1A-1B show localized surface charring c and non-uniform weld regions w in the medial layers m of vessel. Further, FIG. 1B depicts a common undesirable characteristic of prior art welding wherein thermal effects propagate laterally from the targeted tissue causing unwanted collateral (thermal) damage indicated at d.
What is needed is an instrument working end that can utilize Rf energy (i) to transect tissue about a curved path; (ii) to provide a seal in tissue that limits collateral thermal damage; and (iii) to provide a seal or weld in substantially thick anatomic structures and tissue volumes that are not uniform in hydration, density and collagenous content.